Subtraction-Like Effect in an Ant Faced with Numbers of Elements Including a Crossed One

When trained to a number of colored elements of which one was crossed, tested Myrmica sabuleti worker ants reacted essentially to that number of elements excluding the crossed one. They thus apparently subtracted the crossed element, moreover doing so better for fewer numbers of elements. When trained in the same way but tested in front of a number of uncrossed elements equal to the total number of crossed and uncrossed elements seen during training, and at the same time, to the same number of elements without the crossed one as well as to the crossed element only, the ants again reacted essentially to the number of elements minus the crossed one. Again, they did so better for smaller numbers. The ants reacted thus to the visual cue they best saw during training. They also somewhat reacted to the isolated crossed element and better when trained to lower numbers of elements. When trained to a number of uncrossed colored elements and at the same time, to a cue showing the same number of elements, but one crossed and the others uncolored, the tested ants reacted more to the initial total number of colored elements than to the same total number of colored elements minus the crossed one. This showed again that the ants did not really subtract, but reacted to what they the most distinctly saw during training. They also again better reacted in presence of fewer elements.